Stanford, CA. — In a commentary in the September
25, 2007, issue of the Geophysical Research
Letters (GRL), a large team of scientists state
that human-induced carbon dioxide (CO2) emissions
will alter ocean chemistry to the point where it
will violate U.S. Environmental Protection Agency
Quality Criteria [1976] by mid-century if
emissions are not dramatically curtailed now.
This is the first recognition that atmospheric
CO2 emissions will cause ocean waters to violate
EPA water quality criteria.

The paper also says that carbon-dioxide induced
“changes in ocean chemistry within the ranges
predicted for the next decades and centuries
present significant risks to marine biota” and
that “adverse impacts on food webs and key
biogeochemical process” would result.

An international team of twenty five leading
researchers described the evidence to date
regarding the effects of CO2 emissions on the
acidity of the world’s oceans.

“About 1/3 of the CO2 from fossil-fuel burning is
absorbed by the world’s oceans,” explained lead
author Ken Caldeira from the Carnegie Institution
Department of Global Ecology. “When CO2 gas
dissolves in the ocean it makes carbonic acid
which can damage coral reefs and also hurt other
calcifying organisms, such as phytoplankton and
zooplankton, some of the most critical players at
the bottom of the world’s food chain. In
sufficient concentration, the acidity can corrode
shellfish shells, disrupt coral formation, and
interfere with oxygen supply. ”

Most of the research today points to a future
where, in the absence of a major effort to
curtail carbon dioxide emissions, there will be
double the atmospheric concentrations of CO2 (760
parts per million, or ppm) by century’s end.
Atmospheric carbon dioxide concentrations could
reach 500 ppm by mid-century. Pre-industrial
concentrations, by comparison, were 280 ppm and
today’s concentration is about 380 ppm.

The acidity from CO2 dissolved in ocean water is
measured by the pH scale (potential of Hydrogen).
Declines in pH indicate that a solution is more
acidic. The U.S. Environmental Protection Agency
[1976] Quality Criteria for Water state: “For
open ocean waters where the depth is
substantially greater than the euphotic zone, the
pH should not be changed more than 0.2 units
outside the range of naturally occurring
variation Ã…Â ” The euphotic zone goes to a depth of
about 650 feet (200 meters), where light can
still reach and photosynthesis can occur.

“Atmospheric CO2 concentrations need to remain at
less than 500 ppm for the ocean pH decrease to
stay within the 0.2 limit set forth by the U.S.
Environmental Protection Agency [1976],” remarked
Caldeira. “If atmospheric CO2 goes above 500 ppm,
the surface of the entire ocean will be out of
compliance with EPA pH guidelines for the open
ocean. We need to start thinking about carbon
dioxide as an ocean pollutant. That is, when we
release carbon dioxide to the atmosphere, we are
dumping industrial waste in the ocean.”

Keeping atmospheric carbon dioxide concentrations
below 500 ppm level would require a rapid global
transition to a system of energy production and
consumption that releases very little carbon
dioxide to the atmosphere.

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The study was led by Ken Caldeira of Carnegie
Institution’s Department of Global Ecology.
Included are researchers from Norway, the United
Kingdom, France, Australia, Japan, Monaco, and
the United States. Co-authors of the study are:

Richard E. Zeebe, University of Hawaii at Manoa, USA (zeebe@soest.hawaii.edu)

Carnegie’s department of Global Ecology was
founded in 2002 on the campus of Stanford
University. Its staff conducts basic research on
the interactions among Earth’s ecosystems, land,
atmosphere, and oceans to understand how the
interactions shape the behavior of the Earth
system, including its response to future change.
The Carnegie Institution
(www.CarnegieInstitution.org) has been a
pioneering force in basic scientific research
since 1902. It is a private, nonprofit
organization with six research departments
throughout the U.S. Carnegie scientists are
leaders in plant biology, developmental biology,
astronomy, materials science, global ecology, and
Earth and planetary science.
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